'use strict'

var util = require('util')

var splitter = /^(.*?)(?::(eq|(?:(?:first|last)(?!-child)))(?:\((\d+)\))?)(.*)/

exports.wrap = function (Cheerio) {
    function CheerioAdv (selector, context, root, opts) {
        if (!(this instanceof CheerioAdv)) return new CheerioAdv(selector, context, root, opts)

        if (typeof selector === 'string' && splitter.test(selector)) {
            var steps = split(selector)
            var cursor = Cheerio(steps.shift(), context, root, opts)
            return execSteps(cursor, steps)
        }

        return Cheerio.apply(Cheerio, arguments)
    }

    util.inherits(CheerioAdv, Cheerio)

    CheerioAdv.load = function () {
        var $ = Cheerio.load.apply(Cheerio, arguments)

        function AdvInitialize (selector, context, root) {
            if (typeof selector === 'string') return exports.find($, selector, context, root)
            return $.apply(Cheerio, arguments)
        }

        Object.keys($).forEach(function (key) {
            AdvInitialize[key] = $[key]
        })

        return AdvInitialize
    }

    return CheerioAdv
}

exports.find = function ($, selector, context, root) {
    return exports.compile(selector)($, context, root)
}

exports.compile = function (selector) {
    var steps = split(selector)
    selector = steps.shift()

    return function ($, context, root) {
        var cursor = $(selector, context, root)
        return execSteps(cursor, steps)
    }
}

var split = function (selector) {
    var steps = []
    var match = selector.match(splitter)

    while (match) {
        steps.push(match[1])
        steps.push(selectors[match[2]](match[3]))
        selector = match[4].trim()
        match = selector.match(splitter)
    }

    steps.push(selector)

    return steps.filter(function (step) {
        return step !== ''
    })
}

var execSteps = function (cursor, steps) {
    return steps.reduce(function (cursor, step) {
        return typeof step === 'function' ? step(cursor) : cursor.find(step)
    }, cursor)
}

var selectors = {
    eq: function (index) {
        index = parseInt(index, 10)
        return function (cursor) {
            return cursor.eq(index)
        }
    },

    first: function () {
        return function (cursor) {
            return cursor.first()
        }
    },

    last: function () {
        return function (cursor) {
            return cursor.last()
        }
    }
}